//代码清单6－2 Web服务器上的集中写
#include <sys/uio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>

#define BUFFER_SIZE 1024
/* 定义两种HTTP状态码和状态信息*/
static const char* status_line[2] = {"200 OK","500 Internal server error"};

int main(int argc,char* argv[])
{
    if(argc <=3)
    {
        printf("usage: %s ip_address port_number filename\n",basename(argv[0]));
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi(argv[2]);

    /* 将目标文件作为程序的第三个参数传入 */
    const char* file_name = argv[3];

    struct sockaddr_in address;
    bzero(&address,sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET,ip,&address.sin_addr);
    address.sin_port = htons(port);

    int sock = socket(PF_INET,SOCK_STREAM,0);
    assert(sock >=0);

    int ret = bind(sock,(struct sockaddr*)&address,sizeof(address));
    assert(ret !=-1);

    ret = listen(sock,5);
    assert(ret !=-1);

    struct sockaddr_in client;
    socklen_t client_addrlenetght = sizeof(client);
    int connfd = accept(sock,(struct sockaddr*)&client,&client_addrlenetght);
    if(connfd < 0)
    {
        printf("errno is: %d\n",errno);
    }
    else{
        /*用于保存HTTP应答的状态行、头部字段和一个空行的缓存区*/
        char header_buf[BUFFER_SIZE];
        memset(header_buf,'\0',BUFFER_SIZE);
        /*用于存放目标文件内容的应用程序缓存*/
        char* file_buf;
        /*用于获取目标文件的属性，比如是否为目录，文件大小等 */
        struct stat file_stat;
        /*记录目标文件是否是有效文件*/
        bool valid = true;
        /*缓存区header_buf目前已经使用了多少字节的空间*/
        int len = 0;
        if(stat(file_name,&file_stat) < 0)  /*目标文件不存在*/
        {
            valid = false;
        }
        else
        {
            if(S_ISDIR(file_stat.st_mode)) /*目标文件是一个目录*/
            {
                valid = false;
            }
            else if(file_stat.st_mode & S_IROTH) /*当前用户有读取目标文件的权限*/
            {
                /*动态分配缓存区file_buf,并指定其大小为目标文件的大小
                file_stat.st_size加1，然后将目标文件读入缓存区file_buf中
                */
                int fd = open(file_name,O_RDONLY);
                file_buf = new char[file_stat.st_size+1];
                memset(file_buf,'\0',file_stat.st_size +1);
                if(read(fd,file_buf,file_stat.st_size)<0)
                {
                    valid =false;
                }
            }
            else{
                valid = false;
            }
        }

        /*如果目标文件有效，则发送正常的http应答*/
        if(valid)
        {
            /*下面这部分内容HTTP应答的状态行、“Content-Length”头部字段和一个空行依次加入header_buf中*/
            ret = snprintf(header_buf,BUFFER_SIZE-1,"%s %s\r\n",
            "HTTP/1.1",status_line[0]);
            len +=ret;
            ret = snprintf(header_buf+len,BUFFER_SIZE-1-len,
            "Content-Length:%d\r\n",file_stat.st_size);
            len += ret;
            ret = snprintf(header_buf+len,BUFFER_SIZE-1-len,"%s","\r\n");
            /*利用writev将header_buf和file_buf的内容一并写出*/
            struct iovec iv[2];
            iv[0].iov_base = header_buf;
            iv[0].iov_len = strlen(header_buf);
            iv[1].iov_base = file_buf;
            iv[1].iov_len = file_stat.st_size;
            ret = writev(connfd,iv,2);
        }else /*如果目标文件无效，则通知客户端服务器发生了“内部错误”*/
        {
            ret = snprintf(header_buf,BUFFER_SIZE-1,"%s %s\r\n",
                                        "HTTP/1.1",status_line[1]);
            len += ret;
            ret = snprintf(header_buf + len,BUFFER_SIZE-1-len,"%s","\r\n");
            send(connfd,header_buf,strlen(header_buf),0);
        }
        close(connfd);
        delete[] file_buf;
    }
}